1. Field of the Invention
The present invention relates to the field of routers and Internet data traffic. More particularly, the present invention relates to a high-capacity optical router, in which data traffic, such as an IP packet, an Ethernet frame, etc., is switched in an optical frame unit at a high speed.
2. Description of the Related Art
Recently, there has been a sharp increase in the demand for access to data services, such as Internet, moving picture, video on demand (VOD) etc., both by the public and businesses. A high-capacity data traffic ranging from several hundreds of Gb/s to several Tb/s commonly occurs in the network. In order to ensure the efficient switching and routing of such traffic, a high-capacity router/switch having a capacity ranging from several hundreds of Gb/s to several Tb/s is required.
In the past, the implementation of such a high-capacity IP router was simulated by the connected of tens of low capacity IP routers to each other, so that a high-capacity effect has been obtained. However, this solution has problems in that, because all the IP routers make use of from 50% to 50% of their capacity simply to interconnect with each other. Thus, the prior art multiply-connected routers wastes half or more of its bandwidth becomes. In addition, the number of the IP routers can be abruptly increased depending upon the requested capacity of a simulated high-capacity router. For this reason, the necessity for the router/switch to have a capacity as high as possible has constantly been expressed in order to reduce the number of pieces of equipment.
Conventionally, two methods have been mainly used to implement such a high-capacity router.
FIG. 1 illustrates a first method, which utilizes construction of the conventional all-optical router and shows a how a high-capacity router of the prior art would make such an implementation. According to FIG. 1, optical data are switched through a space switch 14 having on-off gate switches 14-3. When a conflict breaks out between the optical data, the conflict is resolved using a tunable wavelength converter and a fiber delay line buffer. In addition, the optical data are switched using the tunable wavelength converter and a wavelength router such as a N×N AWG (Arrayed Waveguide Grating) or the like, and the conflict between the optical data is resolved through the fiber delay line.
The second method is to implement a high-capacity IP router, to which a high speed interface of 10 Gb/s or more is applied. According to this second method, headers of inputted packets are recognized according to a packet to activate an electrical switch, and thereby packet routing/switching is carried out. A conflict between the packets is resolved through an electrical buffer. To this end, through the use of various kinds of terabit routers, the foregoing type of high-capacity IP router of the prior art has been developed.
In the all-optical router approaching method as in FIG. 1, a fiber delay line is used to resolve the conflict between the optical data, in which the conflict is caused by an absence of an optical memory. However, when a length of the optical data is increased as a switching capacity of the optical router is increased, the fiber delay line may have a length that ranges from tens of km to hundreds of km. This rather large range brings about a problem in that the dimensions of the system, as well as its complexity becomes greatly increased.
Additionally, because the fiber delay line makes use of a time delay effect that an optical signal undergoes a time delay in an optical fiber, it is very difficult to control the system, and a signal level difference between the optical data is generated due to a loss of the optical fiber. In most all-optical router approaching methods, many tunable wavelength converters (TWCs) 12 are used to carry out switching or buffering. Each TWC 12 includes a tunable wavelength laser and a plurality of semiconductor optical amplifiers (SOAs). Therefore, there is a problem in that expensive production costs are generated.
Further, the tunable wavelength laser has a stabilized velocity in a range between several ms and tens of ms. This stabilized velocity is too slow to be suitable for the optical router. The all-optical router has a problem in that it is very difficult to carry-out performance monitoring of signal as well as assist in signal regeneration.
In the prior art shown in FIG. 1, a plurality of optical couplers are used. This high usage of optical coverage introduces the disadvantage that the optical data can be vulnerable to a high path loss. In case of an electrical IP router, the forwarding must be carried out by recognizing packet headers according to inputted packet. However, there is a great restriction on processing speed, processing high speed packets at a transmission speed of 10 Gb/s. Up to now, the interface for 40 Gb/s has not been developed.
To process 64 byte packets having a transmission speed of 10 Gb/s or 40 Gb/s with the use of the present technique, a forwarding speed of 15 Mp/s or 60 Mp/s is needed. Additionally, packets that are added or dropped with respect to a lower router as well as packets passing through must be processed, a processing burden of the router is greatly increased, thus bringing about a waste of a processing capacity.
In the high-capacity IP router, a high speed electrical switch must be used. However, such an electrical switch places restrictions on speed and expansibility. Further, when a high-capacity node requiring a capacity of several Tb/s or more is established, tens of high-capacity routers are needed. As a result, the high-capacity node does not only become still more complicated, but also has greatly increased establishing and working costs.